LOS ANGELES Dec 10, 2004 — Bram Cohen didn't set out to upset Hollywood movie studios. But his innovative online file-sharing software, BitTorrent, has grown into a piracy problem the film industry is struggling to handle.

As its name suggests, the software lets computer users share large chunks of data. But unlike other popular file-sharing programs, the more people swap data on BitTorrent, the quicker it flows and that includes such large files as feature films and computer games.

Because of its speed and effectiveness, BitTorrent steadily gained in popularity after the recording industry began cracking down last year on users of Kazaa, Morpheus, Grokster and other established file-sharing software.

The program now accounts for as much as half of all online file-sharing activity, says Andrew Parker, chief technology officer of Britain-based CacheLogic, which monitors such traffic.

"BitTorrent is more of a threat because it is probably the latest and best technological tool for transferring large files like movies," said John Malcolm, senior vice president of anti-piracy operations for the Motion Picture Association of America. "It is unusual, perhaps unique, in that the moment you start downloading you are also uploading," he added. "It's what makes it so efficient."

Cohen created BitTorrent in 2001 as a hobby after the dot-com crash left him unemployed. He says the aim was to enable computer users to easily distribute content online not specifically copyrighted content.

"It seems pretty clear that a lot of people are actively interested in engaging in wanton piracy," said Cohen, 29, of Bellevue, Wash. "As far as I'm concerned, they're just pushing around bits, and what bits it is they're pushing around is not really a concern of mine. There's not much I can do about it."

BitTorrent has proven to be resistant to some of the countermeasures the entertainment industry has taken to sabotage file-sharing, including a process known as file-spoofing in which incomplete or decoy versions of songs or other material are uploaded to discourage piracy.

"Spoofing is very difficult on BitTorrent, if at all possible," said Mark Ishikawa, chief executive of online tracking firm BayTSP Inc. "There's no defense for this one."

Programs such as Kazaa and Morpheus allow users to link their PCs to computer networks and then query a search engine for the file or title they're seeking. The software then churns out a list of other computers sharing the file.

The process is simple and straightforward, which makes it relatively easy to corrupt with spoofed files.

With BitTorrent, however, users don't find whole files. The program seeks out torrent files, also known as seed files, that are hosted by a number of Web sites.

The files on the Web sites are not songs or movies but serve as markers that point the way to other users sharing a given file. BitTorrent then assembles complete files from multiple chunks of data obtained from everyone who is sharing the file.

Attempts to upload bogus files to corrupt the process fail because the BitTorrent program follows a blueprint of the original file when piecing it together.

"It's very difficult for an interdiction company to get in the middle of that system," said Ishikawa, whose company combs file-sharing networks on behalf of Hollywood studios and alerts clients when their movies turn up on the Internet.

Some of the BitTorrent host sites, like SuprNova.org, generate a daily list of new seed files added by users. The site recently had listings for movies such as "Van Helsing" and "Wimbledon," which is not scheduled for release on DVD for another three weeks.

Some sites offer digitized broadcasts of "The Daily Show With Jon Stewart," computer games like "Star Trek: Klingon Academy" and "Half Life 2," e-books on the physics behind an atomic bomb, even footage of kidnap victims in the Middle East.

"A bunch of the different beheadings are online," Ishikawa said.

Downhill Battle, a Worcester, Mass.-based independent music group that has developed its own BitTorrent-based software called Blog Torrent, says the technology is much more than a tool for swapping copyright movies and software (a blog is a Web journal).

"What we're excited about as far as BitTorrent goes is the possibility for people to blog video and blog their own home movies (and) independent films and have a way to distribute them online without having to have a big budget for Web-hosting," said Nicholas Reville, one of the group's directors.

"Bandwidth has been a big barrier," he said. "BitTorrent solved that."

While some of the BitTorrent sites that host seed files have been forced to shut down, many others escape scrutiny because they're only hosting marker files, not copyrighted material.

Malcolm of the MPAA says his organization is not focusing any more or less on BitTorrent than other file-sharing system. He declined to say whether the trade group intends to sue Cohen and wouldn't name any BitTorrent users who may have been included in the entertainment industry's latest wave of lawsuits.

"Anyone who uses BitTorrent and is under the illusion that they are anonymous are sorely mistaken," Malcolm said. "There is no reason why those lawsuits wouldn't include BitTorrent" users.

So far, Cohen said, he has not become a target of the entertainment industry, which has aggressively pursued litigation against other file-sharing software distributors, with mixed success. On Friday, the U.S. Supreme Court agreed to hear an appeal by movie studios and music labels of a ruling that found Grokster Ltd. and StreamCast Networks Inc., the firm behind the Morpheus software, to not be responsible for their customers' online swapping of copyright songs and movies.

For his part, Cohen said he has received just one legal warning, over a computer game that was being distributed using BitTorrent.

"Someone else was doing something with BitTorrent that I had no knowledge of," Cohen said. "It's not being done on any machines I have any control over … what do you want me to do?"

It is often used to download Linux distros as it is an efective way for them to get the software out there. However if can be used for any file type. The basic way it works is you just download chuncks of the file from anyone having it. You can share your chunks before you are done downloading the full file. It takes advantage of the upload speeds most people barely if ever use for more than spyware.

With copyright law, what if say everyone only uploaded a certain percent. I know it sounds like BS, but to get around the current laws.

Say you limit everyone to 10% of a movie or song, then no one would be sharing it in its entirity?

Course they would still get the full file, but no single person would EVER be giving out the entire file. Which means, you would need several seeders, but that is almost always the case.

Also, bitto doesn't leave you open and show you what you have downloaded like most other p2p programs and once you are done upping, simply close that tracker and you won't be going back. I prefer it to my PC sitting online to a large p2p network all day.